Mig brazing-gas shield or not?

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I just purchased a 2 pound spool of silicone-bronze wire (.030) for mig brazing. Can this wire be run on mild steel without a shielding gas?There are special gas mixes for use on galvanized steel that contain Argon,CO2 and Helium. Could I just use my existing Argon/CO2 75/25 mix withoutany problem? What about no gas at all. These braze joints don't have to lookbeautiful. I just want them to be functional and it's not structural or criticalas far as safety goes. I could just mig it with shielded core wire or gas shielded wire, but I'm interested in learning a new process to join metal without puddling. Not damaging galvanized steel while joining it would be a plus for me. I've always enjoyed brazing steel with OA, now I want to try itwith mig.Thanks,Don
Reply:You cannot braze with mig and no you cannot use silicone bronze without a gas.  75/25 is ok but use a gas, helium is not a must.   JohnSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:John,What do you mean when you say you cannot brase with mig?Check out this URL:http://www.cadvision.com/blanchas/54...g-brazing.htmlThey call it mig brazingDon
Reply:They play tricks us, you can do the same by adjusting the solpe and inductance of the power supply and do the same thing.  Look up the Slope and Inductance difinations and then I will explain how they work, but you have to do some work also.   " A Little Extra "              John   SMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:that link calls it a new process from europe---we used it at ford motor in the mid 60's to replace gas brazing----then we replaced it with steel mig using e70s-6 wire.
Reply:Mr. Boat ( you have earned it ), It is not a new process.  Do you know Slope and inductance on a cv power supply.  JohnSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:Slope will limit the amount of current from the machine in dip transfer so that the molten drop from the wire doesn't splatter or blast off the end of the wire. Inductance regulates the number of dips(short circuits) per second. It is anadditional current control i.e. how fast the current rises in the wire tip.Increasing inductance causes a slower rise in current to the tip of the wire, therefore fewer dips per second.Those definitions may be over simplified, but that's my best understanding ofslope and inductance. I think they are useful mostly in dip transfer with lowvoltage and current and small wire.
Reply:I mig braze alot with .023 sil bronze wire and use 100% argon. I gave some small sample spools to some guys at work and they used 75/25 gas with no problems but i didn't try it since i have argon and thats what is recommended...BobLast edited by aametalmaster; 11-11-2007 at 07:39 PM.Bob WrightSalem, Ohio  Birthplace of the Silver & Deming Drillhttp://groups.yahoo.com/group/southbend10k/http://groups.yahoo.com/group/sawking/1999 Miller MM185 w/ Miller 185 Spoolmate spoolgun
Reply:Here's another site where they talk about mig brazing:http://www.mig-welding.co.uk/cast-iron.htmIt's from the UK, so anything's possible.I have read that it's and old process, then I read that it's a new process.I don't know(or care that much), but I would like to know if anyone out therehas tried it without gas and what kind of results they got. I have read that the arc acts like a flux, cleaning the metal before the brazing is deposited.Thanks for that information Bob, that's what I was looking for. It looks like I'll just use my existing 75/25 mix since I can't justify buying a new cylinder of pure Argon.Last edited by dicharry; 11-11-2007 at 07:52 PM.
Reply:Trust me it needs gas. I did forget to turn mine on just once. I tried my wire on some cast with not good results but i think you needed larger dia wire mine just melted off even preheated the casting.  Also there needs to be a little gap between the parts for the wire to flow into since it dosen't melt the parent metal at all. Overlap is fine if its not going to be ground off flush. I welded alot of sheetmetal on my neighbors car and it was great and warpage was almost nil...BobBob WrightSalem, Ohio  Birthplace of the Silver & Deming Drillhttp://groups.yahoo.com/group/southbend10k/http://groups.yahoo.com/group/sawking/1999 Miller MM185 w/ Miller 185 Spoolmate spoolgun
Reply:Originally Posted by dicharrySlope will limit the amount of current from the machine in dip transfer so that the molten drop from the wire doesn't splatter or blast off the end of the wire. Inductance regulates the number of dips(short circuits) per second. It is anadditional current control i.e. how fast the current rises in the wire tip.Increasing inductance causes a slower rise in current to the tip of the wire, therefore fewer dips per second.Those definitions may be over simplified, but that's my best understanding ofslope and inductance. I think they are useful mostly in dip transfer with lowvoltage and current and small wire.
Reply:I don't know also how old the process is but my wire is http://www.crownalloys.com and my little Crown book is 17 years old and the wire is listed there. I did mig braze 30 years ago but i don't know if it was sil bronze wire or phos bronze wire but i used it building up some wear bars...BobBob WrightSalem, Ohio  Birthplace of the Silver & Deming Drillhttp://groups.yahoo.com/group/southbend10k/http://groups.yahoo.com/group/sawking/1999 Miller MM185 w/ Miller 185 Spoolmate spoolgun
Reply:not sure if you'll encounter the problem with silicon bronze mig,but with the OA EUTECTIC POWDER TORCH we found that the brass would penetrate thin mild steel along the grain boundaries of the steel and you would end up with the strength of brass instead of steel. this was on the roof to a-post joint when trying to eliminate body solder.